Method and system for calibrating an imaging system

ABSTRACT

The disclosure relates to a system and method for medical imaging. The method may include: move, by a motion controller, a phantom along an axis of a scanner to a plurality of phantom positions; acquire, by a scanner of the imaging device, a first set of PET data relating to the phantom at the plurality of phantom positions; and store the first set of PET data as an electrical file. The length of an axis of the phantom may be shorter than the length of an axis of the scanner, and at least one of the plurality of phantom positions may be inside a bore of the scanner.

CROSS-REFERENCE OF RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2017/104779, filed on Sep. 30, 2017, which claims priority ofChinese Patent Application No. 201621099638.6, filed on Sep. 30, 2016,Chinese Patent Application No. 201611039000.8, filed on Nov. 21, 2016,and Chinese Patent Application No. 201710308861.X, filed on May 4, 2017.The entire contents of these applications are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure generally relates to a medical system, and morespecifically relates to methods and systems for calibrating a PositronEmission Tomography (PET) system.

BACKGROUND

Medical imaging systems may include a Positron Emission Tomography (PET)system for medical diagnosis or treatment. An object, such as a phantom,may be scanned to obtain PET data. During a performance test and acorrection of the PET system, the phantom may be acquired to irradiateall detector units in the detector. For a PET system with a relativelylong axial length (e.g., 2 meters), a plurality of phantoms may be usedto perform the PET scan, based on which a PET image may bereconstructed. The inhomogeneity of the plurality of phantoms mayintroduce noise to the PET image. There is a need for a system andmethod to solve the problem.

SUMMARY

In a first aspect of the present disclosure, a method for medicalimaging is provided. The method may include one or more of the followingoperations. A phantom may be moved along an axis of a scanner to aplurality of phantom positions. A first set of PET data relating to thephantom at the plurality of phantom positions may be acquired, by ascanner of the imaging device. The length of an axis of the phantom maybe shorter than the length of an axis of the scanner, and at least oneof the plurality of phantom positions may be inside a bore of thescanner. The first set of PET data may be stored as an electrical file.

In some embodiments, the plurality of phantom positions may bedetermined based on a scanning parameter of the scanner and a parameterof the phantom.

In some embodiments, the plurality of phantom positions may bedetermined based on at least one of scan time of the scanner, the lengthof the axis of the scanner, phantom weight and the length of the axis ofthe phantom.

In some embodiments, a PET image may be reconstructed at least based onthe first set of PET data.

In some embodiments, a second set of PET data may be extracted from thefirst set of PET data based on the plurality of phantom positions of thephantom. The second set of PET data may correspond to one or morecoincidence events of the phantom. A first set of attenuation data forthe phantom may be acquired. The first set of attenuation data maycorrespond to part of the axis of the scanner. A second set ofattenuation data for the phantom corresponding to the axis of thescanner may be determined based on the plurality of phantom positionsand the first set of attenuation data. The PET image may bereconstructed based on the second set of PET data and the second set ofattenuation data.

In some embodiments, calibration data may be acquired. The PET image maybe corrected based on the plurality of phantom positions and thecalibration data.

In some embodiments, statistic data of phantom position may be generatedby normalizing the plurality of phantom positions. Statistic data ofnuclide decay may be generated by normalizing nuclide decaycorresponding to the axis of the scanner. The PET image may be correctedbased on the statistic data of phantom position and the statistic dataof nuclide decay.

In some embodiments, the phantom may be placed on a bed, and the motioncontroller may be configured to move the bed to drive the phantom to theplurality of phantom positions.

In a second aspect of the present disclosure, a system for medicalimaging is provided. The system may include a bed configured to supporta phantom, a scanner configured to detect coincidence events related tothe phantom, and a motion controller configured to move the phantomalong the scanner to a plurality of phantom positions. The system mayinclude at least one storage medium and at least one processor. The atleast one storage medium may include a set of instructions. The at leastone processor may be configured to communicate with the at least onestorage medium, wherein when executing the set of instructions, thesystem is configured to perform one or more of the following operations.A first set of PET data relating to a phantom at the plurality ofphantom positions may be acquired, by the scanner of the imaging device.The length of an axis of the phantom may be shorter than the length ofan axis of the scanner, and at least one of the plurality of phantompositions may be inside a bore of the scanner. The first set of PET datamay be stored as an electrical file.

In some embodiments, the motion controller may be further configured tomove the bed to drive the phantom to the plurality of phantom positions.

In some embodiments, the motion controller may include a first motioncontroller. The first motion controller may include a first movingmechanism and a second moving mechanism. The first moving mechanism maybe configured to move the bed in a first direction or a seconddirection. The second moving mechanism may be configured to move thephantom in a third direction. The third direction may be perpendicularto the first direction and the second direction.

In some embodiments, the second moving mechanism may include a supportplate, a first rotating wheel and a second rotating wheel, a firstdriver, and a transmission belt. The first rotating wheel and the secondrotating wheel may be disposed at two ends of the support plate. Thefirst driver may be connected to the first rotating wheel and the secondrotating wheel. The transmission belt may encompass the first rotatingwheel and the second rotating wheel. The transmission belt may extend inthe third direction, and may be connected to the phantom.

In some embodiments, the second moving mechanism may include a supportplate, a screw shaft, a second drive, and a support base. The screwshaft may be disposed on the support plate. The screw shaft may extendin the third direction. The second driver may be connected to an end ofthe screw shaft. The support base attached to the screw shaft. Thesupport base may be connected to the phantom.

In some embodiments, the second moving mechanism may further include aguiding mechanism, and the phantom may be connected to and may movealong the guiding mechanism.

In some embodiments, the second moving mechanism may further include ashield configured to shield radiation from the phantom.

In some embodiments, the motion controller may include a second motioncontroller. The second motion controller may include a moving mechanism.The moving mechanism may include a screw shaft, a slider block, and ashield. The screw shaft may extend along the first direction. An end ofthe screw shaft may be connected to a first driver. The slider block maybe attached to the screw shaft. The slider block may be connected to thephantom. The shield may be configured to accommodate the screw shaft,the slider block and the phantom.

In some embodiments, the second motion controller may further include arotation shaft, a second driver and a rotation arm. The second drivermay be mounted on the slider block and may be connected to an end of therotation shaft. The rotation arm may be configured to rotate the phantomunder a force supplied by the rotation shaft.

In some embodiments, the shield may include a first shield comprising afirst groove. The first groove may extend along the first direction, andthe screw shaft may be disposed inside the first groove.

In some embodiments, the first groove may include a guiding mechanism.The slider block may be configured to move along the guiding mechanism.

In some embodiments, the shield may further include a second shield. Asurface of the second field facing the phantom may include a secondgroove configured to provide a moving passage for the phantom. Thesecond groove may extend in the first direction.

In some embodiments, the system may further include a third grooveconfigured to accommodate the phantom. The third groove may be on adifferent plane from the second groove, and may extend in the firstdirection.

In some embodiments, the third groove may include two closed ends.

In a third aspect of the present disclosure, a non-transitory computerreadable medium is provided. The non-transitory computer readable mediummay include executable instructions that, when executed by at least oneprocessor, cause the at least one processor to effectuate a method. Themethod may include one or more of the following operations. A first setof PET data relating to a phantom at a plurality of phantom positionsmay be acquired, by a scanner of the imaging device. The length of anaxis of the phantom may be shorter than the length of an axis of thescanner, and at least one of the plurality of phantom positions may beinside a bore of the scanner. The first set of PET data may be stored asan electrical file.

Additional features will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the artupon examination of the following and the accompanying drawings or maybe learned by production or operation of the examples. The features ofthe present disclosure may be realized and attained by practice or useof various aspects of the methodologies, instrumentalities andcombinations set forth in the detailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is further described in terms of exemplaryembodiments. These exemplary embodiments are described in detail withreference to the drawings. These embodiments are non-limiting exemplaryembodiments, in which like reference numerals represent similarstructures throughout the several views of the drawings, and wherein:

FIG. 1 is a schematic diagram illustrating an exemplary PET systemaccording to some embodiments of the present disclosure;

FIG. 2 is a block diagram illustrating an exemplary processing engineaccording to some embodiments of the present disclosure;

FIG. 3 is a flowchart illustrating an exemplary process for processingPET data according to some embodiments of the present disclosure;

FIG. 4A is a block diagram illustrating an exemplary motion controllingmodule according to some embodiments of the present disclosure;

FIG. 4B is a block diagram illustrating an exemplary storage moduleaccording to some embodiments of the present disclosure;

FIG. 5 is a flowchart illustrating a method for collecting PET dataaccording to some embodiments of the present disclosure;

FIG. 6 is a flowchart illustrating a method for collecting PET dataaccording to some embodiments of the present disclosure;

FIG. 7 is a block diagram illustrating an exemplary processing moduleaccording to some embodiments of the present disclosure;

FIG. 8 is a flowchart illustrating an exemplary process for processingPET data according to some embodiments of the present disclosure;

FIG. 9 is a block diagram illustrating an exemplary PET imagereconstruction unit according to some embodiments of the presentdisclosure;

FIG. 10 is a flowchart illustrating an exemplary process for processingPET data according to some embodiments of the present disclosure;

FIG. 11 is a flowchart illustrating an exemplary process for correctingthe second set of PET data according to some embodiments of the presentdisclosure; and

FIG. 12 is a flowchart illustrating an exemplary process forreconstructing a PET image according to an embodiment of the presentdisclosure;

FIG. 13 is a flowchart illustrating an exemplary process for controllinga phantom of a medical imaging device with a first motion controlleraccording to an embodiment of the present disclosure;

FIG. 14 is a schematic diagram illustrating a phantom controlling deviceaccording to an embodiment of the present disclosure;

FIG. 15 is a schematic diagram illustrating a phantom controlling deviceaccording to another embodiment of the present disclosure;

FIG. 16 is a schematic diagram illustrating a phantom controlling deviceaccording to another embodiment of the present disclosure;

FIG. 17 is a schematic diagram illustrating a circular motion accordingto some embodiments of the present disclosure.

FIG. 18A is a schematic diagram illustrating a phantom controllingdevice according to an embodiment of the present disclosure;

FIG. 18B is a schematic diagram illustrating an internal structure of afirst shield according to an embodiment of the present disclosure;

FIG. 18C is a schematic diagram illustrating the second shield accordingto an embodiment of the present disclosure;

FIG. 18D is a cross-sectional view illustrating the second shieldaccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant disclosure. However, it should be apparent to those skilledin the art that the present disclosure may be practiced without suchdetails. In other instances, well-known methods, procedures, systems,components, and/or circuitry have been described at a relativelyhigh-level, without detail, in order to avoid unnecessarily obscuringaspects of the present disclosure. Various modifications to thedisclosed embodiments will be readily apparent to those skilled in theart, and the general principles defined herein may be applied to otherembodiments and applications without departing from the spirit and scopeof the present disclosure. Thus, the present disclosure is not limitedto the embodiments shown, but to be accorded the widest scope consistentwith the claims.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise,”“comprises,” and/or “comprising,” “include,” “includes,” and/or“including,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof.

It will be understood that the term “system,” “engine,” “unit,”“module,” and/or “block” used herein are one method to distinguishdifferent components, elements, parts, section or assembly of differentlevel in descending order. However, the terms may be displaced by otherexpression if they achieve the same purpose.

Generally, the word “module,” “unit,” or “block,” as used herein, refersto logic embodied in hardware or firmware, or to a collection ofsoftware instructions. A module, a unit, or a block described herein maybe implemented as software and/or hardware and may be stored in any typeof non-transitory computer-readable medium or other storage device. Insome embodiments, a software module/unit/block may be compiled andlinked into an executable program. It will be appreciated that softwaremodules can be callable from other modules/units/blocks or fromthemselves, and/or may be invoked in response to detected events orinterrupts.

Software modules/units/blocks configured for execution on computingdevices may be provided on a computer-readable medium, such as a compactdisc, a digital video disc, a flash drive, a magnetic disc, or any othertangible medium, or as a digital download (and can be originally storedin a compressed or installable format that needs installation,decompression, or decryption prior to execution). Such software code maybe stored, partially or fully, on a storage device of the executingcomputing device, for execution by the computing device. Softwareinstructions may be embedded in a firmware, such as an EPROM. It will befurther appreciated that hardware modules/units/blocks may be includedin connected logic components, such as gates and flip-flops, and/or canbe included of programmable units, such as programmable gate arrays orprocessors. The modules/units/blocks or computing device functionalitydescribed herein may be implemented as software modules/units/blocks,but may be represented in hardware or firmware. In general, themodules/units/blocks described herein refer to logicalmodules/units/blocks that may be combined with othermodules/units/blocks or divided into sub-modules/sub-units/sub-blocksdespite their physical organization or storage. The description may beapplicable to a system, an engine, or a portion thereof.

It will be understood that when a unit, engine, module or block isreferred to as being “on,” “connected to,” or “coupled to,” anotherunit, engine, module, or block, it may be directly on, connected orcoupled to, or communicate with the other unit, engine, module, orblock, or an intervening unit, engine, module, or block may be present,unless the context clearly indicates otherwise. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

These and other features, and characteristics of the present disclosure,as well as the methods of operation and functions of the relatedelements of structure and the combination of parts and economies ofmanufacture, may become more apparent upon consideration of thefollowing description with reference to the accompanying drawings, allof which form a part of this disclosure. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration and description only and are not intended to limit thescope of the present disclosure. It is understood that the drawings arenot to scale.

Provided herein is a method and system for calibrating an imaging system(e.g., a PET system) and/or generating an image (e.g., a PET image). Thepresent disclosure intends to calibrate the imaging system and/orgenerate the image with a phantom while being placed at a plurality ofphantom positions. By placing the phantom in the plurality of phantompositions at a plurality of time nodes, which may imitate a plurality ofphantoms being disposed at the plurality of phantom positions at a sametime node, radiation related to the phantom may be utilized to calibratethe imaging system and/or generate the PET image, while sparing noisethat may be introduced due to the inhomogeneity of the plurality ofphantoms.

The term “image” used in this disclosure may refer to a 2D image, a 3Dimage, a 4D image, and/or any related data (e.g., PET data, radiationdata corresponding to the PET data). This is not intended to limit thescope of the present disclosure. For persons having ordinary skills inthe art, a certain amount of variations, changes, and/or modificationsmay be deducted under the guidance of the present disclosure.

The term “radiation” used herein may include a particle radiation, aphoton radiation, or the like, or any combination thereof. The particlemay include a positron, a neutron, a proton, an electron, a μ-meson, aheavy ion, or the like, or any combination thereof. The photon mayinclude a gamma photon, an, a beta photon, an X-ray photon, or the like,or any combination thereof. Those variations, changes, and/ormodifications do not depart from the scope of the present disclosure.

FIG. 1 is a schematic diagram illustrating an exemplary PET system 100according to some embodiments of the present disclosure. As shown, thePET system 100 may include a PET scanner 110, a network 120, one or moreterminals 130, a processing engine 140, a storage 150, and a motioncontroller 160.

The PET scanner 110 may include a gantry 111, a bed 112 (or referred toas a scanning table 112), a detecting region 113, and a detector 114.The detector 114 may be mounted on the gantry 111. The bed 112 may bepositioned within a bore of the gantry 111. Specifically, the bed 112may be adapted to be accommodated in a bore enclosed by a plurality ofdetector units of the detector 114 mounted on the gantry 111.

The bed 112 may support an object (e.g., a phantom) for scanning. Theobject (e.g., a phantom) may include a radioactive source that may emitradiology rays. The radiology rays emitted by the phantom may bedetected by one or more detector units of the detector 114. When anobject is supported by a bed 112, the bed 112 may be at a bed location.Merely by way of example, a bed location may be described as a locationof the bed 112 relative to the gantry 111 of the PET system 100 in acertain direction. The certain direction may include, for example, an Xdirection, a Y direction, and/or a Z direction. As used herein, the Xdirection, the Y direction, and the Z direction may represent an X axis,a Y axis, and a Z axis in a coordinate system. Merely by way of example,the X axis and the Z axis may be in a horizontal plane, the X axis andthe Y axis may be in a vertical plane, the Z axis may be along therotational axis of the PET scanner 110. The phantom supported by the bed112 may be at a phantom position. The phantom position may be describedas a spatial location of the phantom relative to the gantry 111 of thePET system 100 in a certain direction. The certain direction mayinclude, for example, an X direction, a Y direction, and/or a Zdirection as illustrated elsewhere in the present disclosure. In someembodiments, the phantom may be placed at a plurality of phantompositions. The plurality of phantom positions may be expressed as below:

-   -   {phantom position 1, phantom position 2, . . . , phantom        position i, . . . , and phantom position N}

In some embodiments, the phantom may be fixed on the bed 112, and aphantom position may correspond to a bed position. In some embodiments,when the bed 112 stops at a bed position, the phantom may be moved onthe bed 112 to stop at a plurality of phantom positions for imaging.Therefore, a bed position may correspond to a plurality of phantompositions.

The detector 114 may detect or collect PET data relating to photons. Thephotons may include a gamma photon, an x-ray photon, or the like, or anycombination thereof. The PET data may include, for example, scanningdata related to the object being scanned (e.g., the phantom). Thescanning data may include, for example, a plurality of coincidenceevents detected by the detector 114 and/or line of response (LOR)scorresponding to the plurality of coincidence events. As used herein, anLOR may refer to a line connecting the detector units that have detectedtwo photons of a coincidence event. Merely by way of example, thedetector 114 may collect a first set of PET data. The first set of PETdata may refer to original PET data (e.g., counting response of thedetector 114) collected by the scanner. In some embodiments, the phantommay be placed at a plurality of phantom positions to generate the firstset of PET data. For example, the first set of PET data may include aplurality sub-sets of PET data, which may be generated by the phantom ata plurality of phantom positions respectively. The plurality sub-sets ofPET data may be expressed as below:

-   -   {PET data 1, PET data 2, . . . , PET data i, . . . , and PET        data N}        wherein each sub-set of PET data of the plurality sub-sets of        PET data may correspond to a phantom position of the plurality        of phantom positions. Merely by way of example, PET data 1 may        correspond to phantom position 1, PET data may correspond to        phantom position 2, PET data i may correspond to phantom        position i, etc. I or N may represent an integer larger than 1.

In some embodiments, at least a portion of the first set of PET data(also referred to as a second set of PET data) may correspond to one ormore coincidence events of the phantom. The second set of PET data maybe extracted from the first set of PET data. The detailed description ofextracting the second set of PET data may be found in FIG. 6 in thepresent disclosure and the description thereof.

In some embodiments, the detector 114 may include one or more detectorunits for detecting scanning data relating to an object (e.g., aphantom), or a portion thereof, located in the detecting region 113. Adetector unit may include a scintillation detector 114 (e.g., a cesiumiodide detector 114), a gas detector 114, etc. The detector 114 may beand/or include a single-row detector 114 and/or a multi-row detector114. In some embodiments, the detector 114 may further send the detectedPET data to the processing engine 140.

The network 120 may include any suitable network that can facilitateexchange of information and/or data (e.g., emission data) for the PETsystem 100.

In some embodiments, one or more components of the PET system 100 (e.g.,the PET scanner 110, the terminal 130, the processing engine 140, thestorage 150, etc.) may communicate information and/or data with one ormore other components of the PET system 100 via the network 120. Forexample, the processing engine 140 may obtain emission data from the PETscanner 110 via the network 120. As another example, the processingengine 140 may obtain user instructions from the terminal 130 via thenetwork 120.

The network 120 may be and/or include a public network (e.g., theInternet), a private network (e.g., a local area network (LAN), a widearea network (WAN)), etc.), a wired network (e.g., an Ethernet network),a wireless network (e.g., an 802.11 network, a Wi-Fi network, etc.), acellular network (e.g., a Long Term Evolution (LTE) network), a framerelay network, a virtual private network (“VPN”), a satellite network, atelephone network, routers, hubs, switches, server computers, and/or anycombination thereof. Merely by way of example, the network 120 mayinclude a cable network, a wireline network, a fiber-optic network, atelecommunications network, an intranet, a wireless local area network(WLAN), a metropolitan area network (MAN), a public telephone switchednetwork (PSTN), a Bluetooth™ network, a ZigBee™ network, a near fieldcommunication (NFC) network, or the like, or any combination thereof. Insome embodiments, the network 120 may include one or more network accesspoints. For example, the network 120 may include wired and/or wirelessnetwork access points such as base stations and/or internet exchangepoints through which one or more components of the PET system 100 may beconnected to the network 120 to exchange data and/or information.

The terminal(s) 130 may include a mobile device 131, a tablet computer132, a laptop computer 133, or the like, or any combination thereof. Insome embodiments, the mobile device 131 may include a smart home device,a wearable device, a mobile device, a virtual reality device, anaugmented reality device, or the like, or any combination thereof. Insome embodiments, the smart home device may include a smart lightingdevice, a control device of an intelligent electrical apparatus, a smartmonitoring device, a smart television, a smart video camera, aninterphone, or the like, or any combination thereof. In someembodiments, the wearable device may include a bracelet, a footgear,eyeglasses, a helmet, a watch, clothing, a backpack, a smart accessory,or the like, or any combination thereof. In some embodiments, the mobiledevice may include a mobile phone, a personal digital assistance (PDA),a gaming device, a navigation device, a point of sale (POS) device, alaptop, a tablet computer, a desktop, or the like, or any combinationthereof. In some embodiments, the virtual reality device and/or theaugmented reality device may include a virtual reality helmet, virtualreality glasses, a virtual reality patch, an augmented reality helmet,augmented reality glasses, an augmented reality patch, or the like, orany combination thereof. For example, the virtual reality device and/orthe augmented reality device may include a Google Glass™, an OculusRift™, a Hololens™, a Gear VR™ etc. In some embodiments, the terminal(s)130 may be part of the processing engine 140.

The processing engine 140 may process data and/or information obtainedfrom the PET scanner 110, the terminal 130, and/or the storage 150.Merely by way of example, the processing engine 140 may process theemission data (e.g., the reference emission data, the working emissiondata, etc.) transmitted from the detector 114 of the PET scanner 110.

In some embodiments, the processing engine 140 may be a single server ora server group. The server group may be centralized or distributed. Insome embodiments, the processing engine 140 may be local or remote. Forexample, the processing engine 140 may access information and/or datastored in the PET scanner 110, the terminal 130, and/or the storage 150via the network 120. As another example, the processing engine 140 maybe directly connected to the PET scanner 110, the terminal 130 and/orthe storage 150 to access stored information and/or data. In someembodiments, the processing engine 140 may be implemented on a cloudplatform. Merely by way of example, the cloud platform may include aprivate cloud, a public cloud, a hybrid cloud, a community cloud, adistributed cloud, an inter-cloud, a multi-cloud, or the like, or anycombination thereof.

The storage 150 may store data, instructions, and/or any otherinformation. In some embodiments, the storage 150 may store dataobtained from the terminal 130 and/or the processing engine 140. In someembodiments, the storage 150 may store data and/or instructions that theprocessing engine 140 may execute or use to perform exemplary methodsdescribed in the present disclosure. In some embodiments, the storage150 may include a mass storage, a removable storage, a volatileread-and-write memory, a read-only memory (ROM), or the like, or anycombination thereof. Exemplary mass storage may include a magnetic disk,an optical disk, a solid-state drive, etc. Exemplary removable storagemay include a flash drive, a floppy disk, an optical disk, a memorycard, a zip disk, a magnetic tape, etc. Exemplary volatileread-and-write memory may include a random access memory (RAM).Exemplary RAM may include a dynamic RAM (DRAM), a double date ratesynchronous dynamic RAM (DDR SDRAM), a static RAM (SRAM), a thyristorRAM (T-RAM), and a zero-capacitor RAM (Z-RAM), etc. Exemplary ROM mayinclude a mask ROM (MROM), a programmable ROM (PROM), an erasableprogrammable ROM (EPROM), an electrically erasable programmable ROM(EEPROM), a compact disk ROM (CD-ROM), and a digital versatile disk ROM,etc. In some embodiments, the storage 150 may be implemented on a cloudplatform. Merely by way of example, the cloud platform may include aprivate cloud, a public cloud, a hybrid cloud, a community cloud, adistributed cloud, an inter-cloud, a multi-cloud, or the like, or anycombination thereof.

In some embodiments, the storage 150 may be connected to the network 120to communicate with one or more other components in the PET system 100(e.g., the processing engine 140, the terminal 130, etc.). One or morecomponents in the PET system 100 may access the data or instructionsstored in the storage 150 via the network 120. In some embodiments, thestorage 150 may be directly connected to or communicate with one or moreother components in the PET system 100 (e.g., the processing engine 140,the terminal 130, etc.). In some embodiments, the storage 150 may bepart of the processing engine 140.

The motion controller 160 may move the phantom to a plurality of phantompositions. The motion controller 160 may move the phantom to theplurality of phantom positions directly. For example, the phantom mayconnect to a motion controller 160 placed on the bed 112. The motioncontroller 160 may move the phantom directly on the bed 112. The motioncontroller 160 may move the phantom to the plurality of phantompositions indirectly. For example, the bed 112 may connect to a motioncontroller 160, and the motion controller 160 may move the bed 112 to aplurality of positions in a certain direction (e.g., the X direction,the Y direction, and/or the Z direction). Accordingly, the phantom beingplaced on the bed 112 may be moved to a plurality of positions in thecertain direction (e.g., the X direction, the Y direction, and/or the Zdirection).

The motion controller 160 may be of various configurations. For example,the motion controller 160 may include a first motion controller and/or asecond motion controller. The first motion controller may move the bed112 and/or the phantom in one or more certain directions. Merely by wayof example, the first motion controller may include a first movingmechanism and a second moving mechanism. The first moving mechanism (orreferred to as a scanning-table driving mechanism) may be configured tomove the bed 112 in a first direction (e.g., the Z direction) or asecond direction (e.g., the Y direction). The second moving mechanism(or referred to as phantom controlling device) may be configured to movethe phantom in a third direction (e.g., the Y direction) perpendicularto the first direction and the second direction. The second motioncontroller may move the phantom in a one or more certain directions(e.g., the Z direction). Exemplary first motion controller, first movingmechanism, second moving mechanism, may be found in FIGS. 13-17 and thedescription thereof. Exemplary second motion controller may be found inFIG. 18 and the description thereof.

FIG. 2 is a block diagram illustrating an exemplary processing engine140 according to some embodiments of the present disclosure. Asillustrated in FIG. 2, the processing engine 140 may include a parameteracquisition module 210, a motion controlling module 220, a dataacquisition module 230, a processing module 240, and a storage module250.

The parameter acquisition module 210 may acquire at least one of ascanning parameter of a scanner (e.g., the scanner of the PET system100) or a parameter of a phantom from one or more components in the PETsystem 100 (e.g., the PET scanner 110, the network 120, the terminal130, and/or the storage 150). The scanning parameter may be configuredto scan a phantom and different configurations of the scanning parametermay cause different results of the scanning of a phantom. In someembodiments, the scanning parameter may be related to the size orstructure of a scanner (e.g., the PET scanner 110 of the PET system100). For example, the scanning parameter may include the length of theaxis of the scanner. In some embodiments, the scanning parameter may bedesignated by a user (e.g., a doctor, a nurse, a patient, etc.). Forexample, the scanning parameter of the scanner may include scan time ofthe scanner. A parameter of the phantom may include phantom weight, thelength of the axis of the phantom, the size of the phantom, etc.

The parameter acquisition module 210 may connect to or communicate withthe motion controlling module 220, and transmit the acquired parameter(e.g., the scanning parameter of the scanner, or the parameter of thephantom) thereto.

The motion controlling module 220 may determine a plurality of phantompositions and/or generate a motion instruction to control the movementof the phantom and/or the bed 112.

The motion controlling module 220 may determine a plurality of phantompositions. In some embodiments, the motion controlling module 220 maydetermine the plurality of phantom positions based on the scanningparameter of the scanner and/or the parameter of the phantom. Merely byway of example, the motion controlling module 220 may determine theplurality of phantom positions based on scan time of the scanner, thelength of the axis of the scanner, phantom weight or the length of theaxis of the phantom. The determined plurality of phantom positions maybe expressed as below:

-   -   {phantom position 1, phantom position 2, . . . , phantom        position i, . . . , and phantom position N}

In some embodiments, the plurality of the phantom positions may ensurethat the axis of the scanner is completely covered by the phantom whilebeing placed in the plurality of phantom positions. Therefore, thescintillator crystals in the detector 114 may be irradiated by thephantom while being placed in the plurality of phantom positions (e.g.,radiation rays generated by the phantom). For example, the plurality ofphantom positions may include a phantom position 1 and a phantomposition 2. When the phantom is placed in the phantom position 1, afirst set of scintillator crystals corresponding to a first part of theaxis of the scanner may be irradiated by radiation rays generated by thephantom. When the phantom is placed in the phantom position 2, a secondset of scintillator crystals corresponding to a second part of the axisof the scanner may be irradiated by radiation rays generated by thephantom. The first set of scintillator crystals and at least part of thesecond set of scintillator crystals may constitute all the scintillatorcrystals in the detector 114. The first part of the axis of the scannerand at least part of the second part of the axis of the scanner maycorrespond to the entire axis of the PET scanner 110. Thus, whileplacing the phantom in the phantom position 1 and the phantom position2, the phantom may cover the axis of the scanner, and the scintillatorcrystals in the detector 114 may be irradiated by radiation raysgenerated by the phantom at the phantom position 1 and the phantomposition 2.

The motion controlling module 220 may generate a motion instruction tocontrol the movement of the phantom and/or the bed 112. As used herein,a movement of the phantom (or the bed 112) may be represented by one ormore parameters, for example, a velocity of the phantom (or the bed112), an accelerated velocity of the phantom (or the bed 112), a movingdirection of the phantom (or the bed 112), a moving time span of thephantom (or the bed 112), a moving range of the phantom (or the bed112), an acceleration range of the phantom (or the bed 112), adeceleration range of the phantom (or the bed 112), or the like, or acombination thereof. In some embodiments, the motion controlling module220 may generate the motion instruction based on a user command. Theuser command may be input by the user through, for example, the terminal130.

The motion controlling module 220 may connect to or communicate with themotion controller 160 or the data acquisition module 230. For example,the motion controlling module 220 may transmit the determined pluralityof phantom positions to the data acquisition module 230. As anotherexample, the motion controlling module 220 may transmit the generatedmotion instruction to the motion controller 160, which may operateaccording to the motion instruction.

The data acquisition module 230 may acquire data and/or information fromthe motion controller 160 and one or more components in the PET system100 (e.g., the PET scanner 110, the network 120, the terminal 130, theprocessing engine 140, and/or the storage 150). The data and/orinformation acquired may include the determined plurality of phantompositions, a first set of PET data, and correction data.

The first set of PET data may refer to original PET data collected bythe scanner. The original PET data may include counting response of thedetector 114. In some embodiments, the first set of PET data maycorrespond to the plurality of phantom positions determined by themotion controlling module 220.

The correction data may be configured to correct a PET image related tothe phantom and/or determine a factor of the detector 114. Merely by wayof example, the correction data may include counting response of eachscintillator crystal of the detector 114, based on which a normalizingfactor for normalizing the detecting efficiency of the detector 114 maybe determined. The counting response of the detector 114 may bedetermined by placing the phantom in a plurality of phantom positions.As another example, the correction data may include a first set ofattenuation data for the phantom, based on which a PET image related tothe phantom may be corrected. As used herein, the first set ofattenuation data for the phantom may refer to attenuation datacorresponding to part of the field of vision (FOV) of the PET system100. The attenuation data may include an attenuation map generated fromthe CT scan data of the phantom. Further, as another example, thecorrection data may include nuclide decay information for the phantom,based on which a PET image related to the phantom may be corrected.

The data acquisition module 230 may transmit the acquired data and/orinformation to the motion controlling module 220, the processing module240, and/or the storage module 250. In some embodiments, the dataacquisition module 230 may transmit the plurality of phantom positions,the first set of PET data, and the correction data to the processingmodule 240. Specifically, for example, the data acquisition module 230may transmit the acquired first set of PET data, the plurality ofphantom positions, and/or the first set of attenuation data for thephantom to the PET image reconstruction unit 241 (shown in FIG. 7) inthe processing module 240. As another example, the data acquisitionmodule 230 may transmit the plurality of phantom positions and thenuclide decay information for the phantom to the correction unit 242(shown in FIG. 7) in the processing engine 140.

The processing module 240 may process information provided by the dataacquisition module 230. In some embodiments, the processing module 240may reconstruct PET images based on the first set of PET data, theplurality of phantom positions, and/or the first set of attenuation datafor the phantom according to a reconstruction algorithm, determine anormalizing factor of the detector 114, and/or perform any otherfunction for image reconstruction in accordance with various embodimentsof the present disclosure. The reconstruction algorithm may include anML-EM (Maximum Likelihood Expectation Maximization), an OSEM (OrderedSubset Expectation Maximization), a RAMLA (Row-Action Maximum LikelihoodAlgorithm), a DRAMA (Dynamic Row-Action Maximum Likelihood Algorithm),or the like, or a combination thereof.

The storage module 250 may store PET data, control parameters, processedPET data, or the like, or a combination thereof. For example, thestorage module 250 may store the algorithms to be employed by theprocessing module 240. As another example, the storage module 250 maystore the first set of PET data acquired from the data acquisitionmodule 230. In some embodiments, the storage may store one or moreprograms and/or instructions that may be executed by the processor(s) ofthe processing engine 140 to perform exemplary methods described in thisdisclosure. For example, the storage may store program(s) and/orinstruction(s) that can be executed by the processor(s) of theprocessing engine 140 to cause the PET system 100 or a portion thereofto acquire PET data and/or to process the PET data, etc. In someembodiments, the storage module 250 may include a mass storage. Forexample, the mass storage may include a magnetic disk, an optical disk,a solid-state drives, etc.

It should be noted that the above description of the processing engine140 is merely provided for the purposes of illustration, and notintended to limit the scope of the present disclosure. For personshaving ordinary skills in the art, multiple variations and modificationsmay be made under the teaching of the present invention. However, thosevariations and modifications do not depart from the scope of the presentdisclosure. For example, the parameter acquisition module 210 and thedata acquisition module 230 may be integrated to a data acquisitionmodule 230, which perform the function of both the parameter acquisitionmodule 210 and the data acquisition module 230.

FIG. 3 is a flowchart illustrating an exemplary process 300 forprocessing PET data according to some embodiments of the presentdisclosure. The process, or a portion thereof, may be implemented on aprocessing engine 140 as illustrated in FIG. 1. For illustrationpurposes, the following description is provided with reference to thePET system 100 as illustrated in FIG. 1. As already described, the PETsystem 100 includes a detector 114 including scintillator crystals.

In 302, the parameter acquisition module 210 may acquire at least one ofa scanning parameter of a scanner or a parameter of a phantom. Thescanning parameter may be configured to scan a phantom and differentconfigurations of the scanning parameter may cause different results ofthe scanning of a phantom. For example, the scanning parameter mayinclude the length of the axis of the scanner, scan time of the scanner,etc. The parameter of the phantom may include phantom weight, the lengthof the axis of the phantom, the size of the phantom, etc.

In 304, the motion controlling module 220 may determine a plurality ofphantom positions based on the at least one of the scanning parameter ofthe scanner or the parameter of the phantom. Merely by way of example,the motion controlling module 220 may determine the plurality of phantompositions based on scan time of the scanner, the length of the axis ofthe scanner, phantom weight or the length of the axis of the phantom.The determined plurality of phantom positions may be expressed as:{phantom position 1, phantom position 2, . . . , phantom position i, andphantom position N}. In some embodiments, the determined plurality ofthe phantom positions may ensure that the axis of the scanner iscompletely covered by the phantom while being placed in the plurality ofphantom positions. Therefore, the scintillator crystals in the detector114 maybe irradiated by the phantom (e.g., radiation rays generated bythe phantom) while being placed in the plurality of phantom positions.

In 306, the data acquisition module 230 may acquire a first set of PETdata produced by the phantom at the plurality of phantom positions. Thefirst set of PET data may refer to a set of original PET data collectedby the scanner while the phantom is placed at the plurality of phantompositions. The set of original PET data may include a plurality ofsub-sets of PET data, which may be generated by the phantom at theplurality of phantom positions respectively. The plurality sub-sets ofPET data may be expressed as: {PET data 1, PET data 2, . . . , PET datai, . . . , and PET data N}.

In 308, the processing module 240 may process the acquired first set ofPET data. In some embodiments, the processing module 240 may process theacquired first set of PET data (e.g., the PET data 1, the PET data 2,etc.) corresponding to the respective phantom positions (e.g., thephantom position 1, the phantom position 2, etc.) to generate a PETimage. In some embodiments, the processing module 240 may process theacquired first set of PET data to determine normalizing factors of adetector 114. For example, the acquired first set of PET data mayinclude counting responses (e.g., a first counting response, a secondcounting response, an ith counting response, an nth counting response,etc.) of scintillator crystals (e.g., a first scintillator crystal, asecond scintillator crystal, an ith scintillator crystal, an nthscintillator crystal, etc.) of the detector 114. The normalizing factorof a certain scintillator crystal may be determined based on thecounting response of the scintillator crystal. For example, thenormalizing factor of the ith scintillator crystal Mi may be determinedby:

$\begin{matrix}{{M_{i} = \frac{\sum\limits_{i}^{M}{D_{i}/M}}{D_{i}}},} & (1)\end{matrix}$wherein M may represent the number of the scintillator crystals, Di mayrepresent the counting response of the ith scintillator crystal, and imay represent an integer larger than 1.

It should be noted that the flowchart described above is provided forthe purposes of illustration, not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be reduced to practice in thelight of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure.For example, a step in which the first set of PET data may be stored maybe added between operation 306 and 308.

FIG. 4A is a block diagram illustrating an exemplary motion controllingmodule 220 according to some embodiments of the present disclosure. Asillustrated, the motion controlling module 220 may include a bed motioncontrolling unit 410.

The bed motion controlling unit 410 may control the movement of thescanning table 112 (or referred to as the bed 112) and adjust theposition of the scanning table 112 in real time. For example, the bedmotion controlling unit 410 may drive the scanning table 112 to movealong the rotational axis of the PET scanner 110.

In some embodiments, the bed motion controlling unit 410 may control themovement of the scanning table 112 based on the scanning parameters ofthe PET scanner 110, the information of the phantom and/or theinformation of the scanning table 112. Specifically, the bed motioncontrolling unit 410 may perform logical calculations based on theacquired scanning parameters of the PET scanner 110, the information ofthe phantom and/or the information of the scanning table 112 to obtainmotion control logic of the scanning table 112. The motion control logicof the scanning table 112 may relate to, for example, a movement rangeof the scanning table 112 along the axis (Z direction) of the detector114, a movement speed of the scanning table 112 andacceleration/deceleration positions of the scanning table 112. As usedherein, an acceleration position of the scanning table 112 may relate tolocation at which the scanning table 112 starts to accelerate. Adeceleration position of the scanning table 112 may relate to locationat which the scanning table 112 starts to decelerate. In someembodiments, to ensure the detector 114 to collect enough phantom data(or referred to as scanning data related to the phantom), the scanningtime of the PET system 100 to the phantom may be increased, the scanningtable 112 may perform reciprocating motions. The number of times ofreciprocating motion of the scanning table 112 may be adjusted andcontrolled by the motion control logic of the scanning table 112, whichis calculated by the bed motion controlling unit 410. It should be notedthat the bed motion controlling unit 410 may control the scanning table112 to move continuously during a certain time interval or move at auniform velocity. The bed motion controlling unit 410 may also controlthe scanning table 112 to move dis-continuously during at least onecertain time interval or at a non-uniform velocity. It may be within theintent of the present disclosure to control the movement of the scanningtable 112 during the scanning process, to ensure predetermined detectorunits to detect the phantom (or the scanning data related to thephantom). As used herein, the predetermined detector units may refer toone or more detector units of which the detecting abilities are to betested. The predetermined detector units may be designated by a user orthe PET system 100. The predetermined detector units may include one ormore detector units. For example the predetermined detector units mayinclude all detector units of the detector 114.

FIG. 4B is a block diagram illustrating an exemplary storage module 250according to some embodiments of the present disclosure. As illustrated,the storage module 250 may include a PET scan data unit 420. The PETscan data unit 420 may store the scanning data related to the phantom,the position information of the scanning table 112, and/or the positionor length information of the phantom.

FIG. 5 is a flowchart illustrating a method for collecting PET data (orreferred to as a PET data collection method) according to someembodiments of the present disclosure. As shown in FIG. 5, the methodmay include one or more steps as illustrated below.

In 502, a phantom may be placed on the scanning table 112, and thelength of the axis of the phantom may be shorter than the length of theaxis of FOV of the detector 114.

In 504, the scanning table 112 may be controlled to drive the phantom tomove along the axis of FOV of the detector 114. Meanwhile, the detector114 may be used to collect coincidence events from the phantom.

In the PET data collection method according to the present disclosure,the predetermined detector units may be irradiated by the phantom bycontrolling a movement of the scanning table 112 during the collectionrelated to the phantom. When the predetermined detector units includeall the detector units of the detector 114, the collected data by allthe detector units of the detector 114 may be used to determine anormalizing factor and generate a reconstructed PET image. Thus, in thePET data collection method according to the present disclosure, bycontrolling the movement of the scanning table 112, most of the axialFOV, or even entire axial FOV of the detector 114 may be covered by ashort phantom (e.g., a phantom with an axis shorter than the axis of thePET scanner 110). In conclusion, via the PET data collection methodaccording to the present disclosure, a phantom (the length of the axisof the phantom may be shorter than the length of the axis of FOV of thedetector 114) may be used to facilitate the predetermined detector unitsin the detector 114 and even all detector units to collect data of thephantom.

With the scanning method according to the present disclosure, for thelong axial PET system 100, a single phantom with an axial length shorterthan the axial length of FOV of the detector 114 may be used tofacilitate the predetermined detector units to collect data of thephantom and ensure the radiation uniformity of the phantom.

Further, data obtained by the scanning method of a PET system 100according to the present disclosure may be applied to a PET imagereconstruction. The reconstructed PET image may further be used toanalyze the PET system 100. The data obtained by the scanning methodaccording to the present disclosure may be utilized to generate thenormalizing factor of the detector efficiency.

FIG. 6 is a diagram illustrating a method for collecting PET dataaccording to an embodiment of the present disclosure. The scanningmethod of the PET system 100, in some embodiments will be furtherdescribed below in combination with FIG. 1, FIG. 3 and FIG. 6.

In step 502, a phantom may be placed on the scanning table 112 and thelength of the axis of the phantom may be shorter than the length of theaxis of FOV of the detector 114.

Referring to FIG. 1, the PET system 100 may include a detector 114 and ascanning table 112. During a scan of the PET system 100, the phantom maybe placed on the scanning table 112. With a movement of the scanningtable 112, the phantom may be moved into the FOV of the detector 114 sothat the phantom may be scanned by the detector 114 to collectcoincidence events generated from the phantom. Further, the detector 114may include a plurality of detector units arranged in a circular shape.The coincidence events within the FOV of the detector 114 may bedetected by the plurality of detector units 111.

In step 504, the scanning table 112 may be controlled to drive thephantom to move along the axis of FOV of the detector 114. Meanwhile,the detector unit may be used to collect coincidence events from thephantom. Thus, during the data collection process, the phantom may bemoved along the axis to ensure that the predetermined detector units areirradiated by the phantom.

Further, when the scanning table 112 is controlled to move with thephantom along the axis of the PET scanner 110, the movement of thescanning table 112 may be specifically controlled based on scanningparameters of the PET scanner 110. The scanning parameters of the PETscanner 110 may include a scanning time and/or the length of the axis ofFOV of the detector 114 (e.g., the Z direction shown in FIG. 1).Further, when the scanning table 112 is controlled to move with thephantom along the axis of the PET scanner 110, the scanning table 112may also be controlled to move with the phantom based on information ofthe phantom. The information of the phantom may include the length,position and weight of the phantom, etc. Specifically, the informationof the phantom may be obtained by a Computed Tomography (CT) image ofthe phantom. The CT image of the phantom may be obtained by CT scanningof the phantom.

The phantom may be placed on the scanning table 112 and may be movedalong with the movement of the scanning table 112. When the scanningtable 112 is controlled to move with the phantom along the axis of thePET scanner 110, information of the scanning table 112 may be furthercombined to control the movement of the phantom along the axis of thePET scanner 110 (e.g., the Z direction shown in FIG. 1) and along adirection perpendicular to the axis (e.g., the Y direction shown in FIG.1). In some embodiments, the information of the scanning table 112 maybe a deformation factor of the scanning table 112 estimated by adeformation curve of the scanning table 112. Specifically, thedeformation factor of the scanning table 112 may include the deformationfactor of the scanning table 112 in the height direction, the directionperpendicular to the ground floor (e.g., the Y direction shown in FIG.1). It may be possible to adjust the height position of the scanningtable 112 in real time by applying the deformation factor of thescanning table 112 to the height direction. In some embodiments, theheight position of the scanning table 112 may be adjusted dynamically ina manner to ensure that the phantom (or a certain point of the phantom)moves along the axis of the PET scanner (e.g., the Z direction shown inFIG. 1).

During the scanning of the phantom by the detector 114, the movement ofthe scanning table 112 may be controlled. In some embodiments, thescanning table 112 may be moved to a plurality of bed positions. As aresult, the phantom placed on the scanning table 112 may be moved to aplurality of phantom positions. Thus, for a PET system 100 with a longaxial length, the predetermined detector units may be irradiatedrespectively by a short phantom (e.g., a phantom with an axis shorterthan the length of the axial FOV of the detector 114) placed at theplurality of phantom positions. In some embodiments, most or all of thedetector units in the detector 114 may be irradiated when scanning witha short phantom at the plurality of phantom positions to ensure that thephantom cover most of the axial FOV (e.g., 80%) or even the entire axialFOV of the detector 114.

As described above, when the movement range of the phantom along theaxis of the PET scanner 110 corresponds to an axial length larger thanor equal to the length of the axis of FOV of the detector 114, theirritation of phantom may completely cover the entire axial FOV of thedetector 114, and thus, all detector units of the detector 114 maycollect data of the phantom. In some embodiments, the data collected bythe detector units (e.g., all detector units of the detector 114) may befurther used for the normalization correction (e.g., determining anormalizing factor) or PET image reconstruction. In addition, since alldetector units collect data based on a uniform phantom rather than aphantom formed by splicing, for example, a few sub-phantoms, thecoincidence events detected by all detector units are statistically thesame. Therefore, a more accurate normalizing factor and a more accuratereconstructed PET image may be obtained, compared with that generatedwith a phantom that is spliced by a few sub-phantoms. As a result, theperformance of the PET system 100 may be tested and the PET system 100may be corrected more accurately.

FIG. 7 is a block diagram illustrating an exemplary processing module240 according to some embodiments of the present disclosure. As shown,the processing module 240 may include a PET image reconstruction unit241 and a correction unit 242. The correction unit 242 may include anaxial counting correction sub-unit 2421.

The PET image reconstruction unit 241 may be configure to reconstruct aPET image based on the coincidence events detected by the detectorunits. The PET image reconstruction unit 241 may reconstruct a PET imagebased on the first set of PET data, the plurality of phantom positions,and/or the first set of attenuation data for the phantom acquired fromthe data acquisition module 230. Merely by way of example, the PET imagereconstruction unit 241 may be used to extract valid scanning data basedon position of the phantom and to reconstruct PET image in conjunctionwith attenuation information for the phantom within the entire axialFOV. In some embodiments, the PET image reconstruction unit 241 maytransmit the generated PET image to the correction unit 242.

The correction unit 242 may correct the generated PET image and/ordetermine a normalizing factor based on correction data (e.g., first setof attenuation data for the phantom, counting response of eachscintillator crystal of the detector 114, and the nuclide decayinformation for the phantom) and the plurality of phantom positions fromthe data acquisition module 230. For example, the correction unit 242may correct the reconstructed PET image based on the plurality ofphantom positions and the nuclide decay information for the phantom. Tocorrect the reconstructed PET image, the correction unit 242 maygenerate statistic data of phantom position by normalizing a pluralityof phantom positions, generate statistic data of nuclide decay bynormalizing nuclide decay, and further correct the PET image based onthe statistic data of phantom position and the statistic data of nuclidedecay. The plurality of phantom positions and the nuclide decay maycorrespond to the FOV of the detector 114. As another example, thecorrection unit 242 may correct the reconstructed PET image based on thefirst set of attenuation data for the phantom and the plurality ofphantom positions. As another example, the correction unit 242 maydetermine a normalizing factor for normalizing the detecting efficiencyof the detector 114 based on the counting response of each scintillatorcrystal of the detector 114. The correction unit 242 may correct anaxial count of the detector 114. For example, as illustrated, thecorrection unit 242 may include an axial counting correction sub-unit2421. The axial counting correction sub-unit 2421 may be used to performan axial count correction based on statistic information about thescanning table position and statistic information about the nuclidedecay within the axial FOV, in conjunction with the reconstructed PETimage, to improve the image deviation that may be caused by the movementof the scanning table 112 and the nuclide decay.

It should be noted that the above description of the processing module240 is merely provided for the purposes of illustration, and notintended to limit the scope of the present disclosure. For personshaving ordinary skills in the art, multiple variations and modificationsmay be made under the teaching of the present invention. However, thosevariations and modifications do not depart from the scope of the presentdisclosure. For example, the correction unit 242 may be omitted and thefunction of the correction unit 242 may be realized by the imagereconstruction unit.

FIG. 8 is a flowchart illustrating an exemplary process 800 forprocessing PET data according to some embodiments of the presentdisclosure.

In 802, the PET image reconstruction unit 241 may reconstruct a PETimage at least based on the acquired first set of PET data. For example,the PET image reconstruction unit 241 may reconstruct the PET imagebased on the acquired first set of PET data and the plurality of phantompositions corresponding to the first set of PET data for the phantom.One or more reconstruction algorithms may be employed to reconstruct thePET image. Exemplary reconstruction algorithms may be illustratedelsewhere in the present disclosure.

In 804, the correction unit 242 may acquire correction data. Forexample, the correction unit 242 may acquire the first set ofattenuation data for the phantom. As another example, the correctionunit 242 may acquire the nuclide decay information for the phantom.

In 806, the correction unit 242 may correct the reconstructed PET imagebased on the plurality of phantom positions and the correction data. Forexample, the correction unit 242 may correct the reconstructed PET imagebased on the plurality of phantom positions and the nuclide decayinformation for the phantom. As another example, the correction unit 242may correct the reconstructed PET image based on the first set ofattenuation data for the phantom and the plurality of phantom positions.

It should be noted that the flowchart described above is provided forthe purposes of illustration, not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be reduced to practice in thelight of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure.For example, a step in which the correction data may be stored may beadded to the process 800.

FIG. 9 is a block diagram illustrating an exemplary PET imagereconstruction unit 241 according to some embodiments of the presentdisclosure. As illustrated, the PET image reconstruction unit 241 mayinclude a valid data extraction sub-unit 910, an attenuationdetermination sub-unit 920, and an image reconstruction sub-unit 930.

The valid data extraction sub-unit 910 may extract the second set of PETdata (or referred to as valid scanning data) from the first set of PETdata. As described above, the first set of PET data may refer tooriginal PET data collected by the detector units at the plurality ofphantom positions (e.g., phantom position 1, phantom position 2, etc.).The original PET data may include valid scanning data corresponding tothe phantom and invalid PET data not corresponding to the phantom.Merely by way of example, when the phantom is placed at a certainphantom position of the plurality phantom positions, scanning datacorresponding to the phantom may be detected by a certain number ofdetector units of the detector 114 that are within a spatial rangerelated to the phantom position. Meanwhile, one or more detector unitsbeyond the spatial range may detect data not relating to the phantom (orreferred to as invalid scanning data). The valid data extractionsub-unit 910 may extract the valid scanning data (or referred to as thesecond set of PET data) from the first set of PET data based on thecorresponding phantom position. Merely by way of example, for each of atleast one phantom position of the plurality of phantom positions, thevalid data extraction sub-unit 910 may determine data collected by thedetector units within a predetermined spatial range related to thephantom position to be valid scanning data and extract the determinedvalid scanning data from the first set of PET data. The extracted validscanning data corresponding to the plurality of phantom positions mayconstitute the second set of PET data. In some embodiments, the validdata extraction sub-unit 910 may transmit the extracted second set ofPET data to the image reconstruction sub-unit 930.

The attenuation determination sub-unit 920 may determine a second set ofattenuation data for the phantom. As used herein, the second set ofattenuation data for the phantom may to attenuation data correspondingto the entire FOV of the PET system 100. In some embodiments, theattenuation determination sub-unit 920 may determine the second set ofattenuation data for the phantom based on the plurality of phantompositions and the first set of attenuation data which corresponds topart of the FOV of the PET system 100. In some embodiments, theattenuation determination sub-unit 920 may further employ a relationshipbetween the phantom position and the attenuation data may to determinethe second set of attenuation data for the phantom. In some embodiments,the attenuation determination sub-unit 920 may transmit the determinedsecond set of attenuation data for the phantom to the imagereconstruction sub-unit 930.

The image reconstruction sub-unit 930 may reconstruct a PET image basedon the second set of PET data and the second set of attenuation data.For example, the image reconstruction sub-unit 930 may reconstruct thePET image based on the second set of PET data. As another example, theimage reconstruction sub-unit 930 may reconstruct the PET image based onthe second set of PET data and the second set of attenuation data forthe phantom. The image reconstruction sub-unit 930 may employ an imagereconstruction algorithm to reconstruct the PET image. Exemplary imagereconstruction algorithms may be illustrated elsewhere in the presentdisclosure.

It should be noted that the above description of the PET imagereconstruction unit 241 is merely provided for the purposes ofillustration, and not intended to limit the scope of the presentdisclosure. For persons having ordinary skills in the art, multiplevariations and modifications may be made under the teaching of thepresent invention. However, those variations and modifications do notdepart from the scope of the present disclosure. For example, the validdata extraction sub-unit 910 may be omitted and the function of thevalid data extraction sub-unit 910 may be realized by the imagereconstruction sub-unit 930.

FIG. 10 is a flowchart illustrating an exemplary process 1000 forprocessing PET data according to some embodiments of the presentdisclosure.

In 1002, the valid data extraction sub-unit 910 may extract a second setof PET data from first set of PET data based on a plurality of phantompositions of a phantom. The first set of PET data may be collected atthe plurality of phantom positions. The second set of PET data maycorrespond to one or more coincidence events of the phantom. The validdata extraction sub-unit 910 may extract the second set of PET data fromthe first set of PET data based on the corresponding phantom position.Merely by way of example, for each of at least one phantom position ofthe plurality of phantom positions, the valid data extraction sub-unit910 may extract a set of data collected by the detector units within apredetermined spatial range relating to the phantom position. Theextracted plurality sets of data, which may correspond to the at leastone phantom position of the plurality of phantom positions, mayconstitute the second set of PET data.

In 1004, the attenuation determination sub-unit 920 may acquire a firstset of attenuation data for the phantom, the first set of attenuationdata corresponding to part of FOV of an imaging device

In 1006, the attenuation determination sub-unit 920 may determine asecond set of attenuation data for the phantom corresponding to the FOVof the imaging device based on the plurality of phantom positions andthe first set of attenuation data. For example, the second set ofattenuation data for the phantom may correspond to the phantom position1 and phantom position 2. The first set of attenuation data for thephantom may correspond to the phantom position 1. The attenuationdetermination sub-unit 920 may fill attenuation data for the phantomcorresponding to the phantom position 2 based on the first set ofattenuation data for the phantom, the phantom position 1 and the phantomposition 2, which may further constitute the second set of attenuationdata for the phantom with the first set of attenuation data for thephantom.

In 1008, the image reconstruction sub-unit 930 may reconstruct a PETimage based on the second set of PET data and the second set ofattenuation data. An image reconstruction algorithm may be employed toreconstruct the PET image. Exemplary image reconstruction algorithms maybe illustrated elsewhere in the present disclosure.

It should be noted that the flowchart described above is provided forthe purposes of illustration, not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be reduced to practice in thelight of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure.For example, operations 1004 and 1006 may be omitted, and the PET imagemay be reconstructed based on the second set of PET data.

FIG. 11 is a flowchart illustrating an exemplary process 1100 forcorrecting a PET image according to some embodiments of the presentdisclosure. The process may be executed by the correction unit 242.

In 1002, statistic data of phantom position may be generated bynormalizing a plurality of phantom positions corresponding to FOV of animaging device. A detector 114 of the imaging device may collect PETdata related to the phantom while being placed at the plurality ofphantom positions. While the phantom moves amongst the plurality ofphantom positions, the phantom may accelerate or decelerate, thusintroducing noise to the PET data collected by the detector 114. Thecorrection unit 242 may normalize the plurality of phantom positions toreduce the introduced noise. A normalizing method may be employed tonormalize the plurality of phantom positions.

In 1104, statistic data of nuclide decay may be generated by normalizingnuclide decay corresponding to the FOV. In some embodiments, thecorrection unit 242 may extract a plurality sets of nuclide decayinformation corresponding to the plurality of phantom positionscorresponding to the FOV from the nuclide decay corresponding to theFOV, respectively. The extracted plurality sets of nuclide decayinformation may be normalized to determine the statistic data of nuclidedecay. A normalizing method may be employed to normalize the pluralityof phantom positions.

In 1106, the second set of PET data may be corrected based on thestatistic data of phantom position and the statistic data of nuclidedecay. Merely by way of example, the correction unit 242 may perform anaxial count correction on the second set of PET data based on thestatistic data of phantom position and statistic data of nuclide decay.

It should be noted that the flowchart described above is provided forthe purposes of illustration, not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be reduced to practice in thelight of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure. Inoperation 1104, the first set of PET data rather than the second set ofPET data may be corrected based on the statistic data of phantomposition and the statistic data of nuclide decay.

The present disclosure also provides a method for reconstructing the PETimage. FIG. 12 is a flowchart illustrating an exemplary process forreconstructing a PET image according to an embodiment of the presentdisclosure. As shown in FIG. 12, the method of reconstructing the PETimage may include the following steps.

In 1202, scanning data of the phantom may be collected by using the PETdata collection method described above. In some embodiments, in theprocess of collecting data of the phantom by the detector 114, amovement of the scanning table 112 may be controlled so that thepredetermined detector units may be irradiated. The PET data collectionmethod may be specified as described above and will not be describedhere. In some embodiments, the movement range of the phantom along theaxis may correspond to an axial length larger than or equal to thelength of the axis of FOV of the detector 114 so that all detector unitsmay collect data of the phantom.

Position information of the scanning table 112 may be generated whilethe scanning table 112 is moved. Scanning data may be generated whilethe detector 114 is detecting coincidence events. The scanning data mayinclude, for example, a plurality of coincidence events detected by thedetector 114 and line of response (LOR)s corresponding to the pluralityof coincidence events. As used herein, an LOR may refer to a line thatconnects the detector units that have detected two gamma photons of acoincidence event.

In some embodiments, the generated position information of the scanningtable 112 and the scanning data related to the phantom may be furtherstored in a storage. In some embodiments, corresponding data may be reador retrieved from the storage during the subsequent PET imagereconstruction.

In 1204, the position information of the phantom may be obtained basedon the position information of the scanning table 112.

During the data collection process of the phantom, since the length ofthe axis of the phantom is shorter than the length of the axis of FOV ofthe detector 114, at a certain time point, some detector units may beable to collect the scanning data of the phantom while the otherdetector units, which may not be irradiated by the phantom, may collectscanning data that does not correspond to the phantom. The scanning datacorresponding to the phantom may also be referred to as valid scanningdata, and the scanning data not corresponding the phantom may also bereferred to as invalid data. An image reconstruction should be based onthe scanning data of the phantom (e.g., valid scanning data). Therefore,it may be necessary to extract valid scanning data corresponding to thephantom and discard invalid scanning data that does not correspond tothe phantom to generate a more accurate PET image. In some embodiments,the valid scanning data corresponding to the phantom may be determinedbased on the position information of the scanning table 112 at thecorresponding time point. In some embodiments, the position informationof the phantom may be obtained based on the position information of thescanning table 112 to further extract the valid scanning datacorresponding to the phantom.

In some embodiments, the corresponding scanning data may be extractedfrom the collected scanning data based on the position information ofthe phantom to perform the PET image reconstruction.

As described above, after obtaining the position information of thephantom, the valid scanning data corresponding to the phantom may beextracted. In some embodiments, the scanning data related to the phantommay be stored in the PET scan data unit 420, from which thecorresponding scanning data may be extracted based on the positioninformation of the phantom. In some embodiments, the correspondingscanning data may be determined based on the position information of thephantom and the length of the phantom.

Specifically, as shown in FIG. 12, the process of acquiring the validscanning data corresponding to the phantom and perform the PET imagereconstruction based thereon may include one or more of the followingoperations.

In step 1206, attenuation information for the phantom within the entireaxial FOV may be obtained based on attenuation information for thephantom and the position information of the scanning table 112. Theattenuation information for the phantom may be acquired, for example, byCT scanning. For example, CT scanning data of the phantom may beacquired by the CT scanning, based on which an attenuation map, orattenuation information for the phantom may be acquired.

As described above, in some embodiments, the length of the axis of thephantom may be shorter than the length of the axis of FOV of thedetector 114, and the attenuation information for the phantom within theentire axial FOV may not be acquired during the CT scanning of thephantom, which may be performed to acquire the attenuation informationfor the phantom. Thus, in some embodiments according to the presentdisclosure, the position information of the scanning table 112 and theknown attenuation information for the phantom (e.g., attenuationinformation corresponding to part of the axis of FOV of the detector114) may be combined to fill the corresponding position in the axialscanning area with the corresponding attenuation information for thephantom, to acquire the attenuation information for the phantom withinthe entire axial FOV.

In 1208, a PET image reconstruction may be performed with theattenuation information for the phantom within the entire axial FOV, togenerate a reconstructed PET image within the entire axial FOV.

In some embodiments, during the PET image reconstruction process, thevalid scanning data may be extracted based on the position informationof the phantom. Further, a PET image may be reconstructed based on theattenuation information for the phantom and the corresponding scanningdata (e.g., the extracted valid scanning data).

The PET image reconstruction method may include, for example, a filteredback projection (FBP) or an ordered subset expectation-maximization(OSEM).

It should be noted that the recited order of the operations in FIG. 12is not intended to limit the claimed process. For example, the sequenceof the step in which the information for the phantom and the step inwhich the valid scanning data may be extracted may be exchanged, with apremise that the attenuation information for the phantom and the validscanning data are available at the time of performing the PET imagereconstruction.

In some embodiments, the method of reconstructing the PET image furthermay include the following steps:

In step 1210, the statistic information of scanning table position andthe statistic information of the nuclide decay may be obtained bynormalizing the scanning table positions within the axial FOV and thenuclide decay within the axial FOV of the detector 114, respectively.

The statistic information of the scanning table position may be obtainedby extracting and normalizing the position information of the scanningtable 112 and the position or length information of the phantom storedin the PET scan data unit 420. During the data collection process, themovement of the scanning table 112 may drive the phantom to move. Insome embodiments, when the scanning table 112 moves, the scanning table112 may accelerate or decelerate, which may drive the phantom toaccelerate or decelerate accordingly. In some embodiments, thoroughnormalizing the corresponding position information of the scanning table112, the position of the phantom (the position information of thephantom on the scanning table 112) and/or the length of the phantom ateach time point, image differences that may be generated due to theacceleration or deceleration of the scanning table 112 and other factorsduring the movement of the scanning table 112 may be corrected toreconstruct a more accurate PET image.

Similarly, the statistic information of the nuclide decay may also beobtained by extracting nuclide decay information at the correspondingtime point from the PET scan data unit 420 based on the positioninformation of the scanning table 112 and by normalizing the nuclidedecay within the axial FOV of the detector 114. That is, due to theradioactive decay of the nuclide, the nuclide decay informationextracted based on the position information of the scanning table 112 ateach time point may be normalized, to avoid a deviation that thereconstructed image may have due to the nuclide decay.

In 1212, an axial count correction may be performed based on thestatistic information of the scanning table position and the statisticinformation of the nuclide decay within the axial FOV, and thereconstructed PET image, to obtain a corrected PET image of the phantomwithin the entire axial FOV.

After operation 1208, in which the reconstructed PET image may beobtained, the reconstructed PET image may be axially corrected byfurther combining the statistic information of the scanning tableposition and the statistic information of the nuclide decay within theaxial FOV to eliminate the image differences due to the acceleration,deceleration of the scanning table 112 and other factors, and further toavoid the impact of the nuclide decay on the reconstructed image. Thus,a more accurate corrected reconstructed PET image of the phantom withinthe entire axial FOV may be obtained. In this way, the reconstructed PETimage may be analyzed to further obtain the performance and workingcondition of the PET system 100. For example, the axial uniformity ofthe PET system 100 may be verified based on the reconstructed PET image.

In some embodiments, the PET image may be reconstructed by using thedata of the phantom collected by all detector units, so that the qualityanalysis may be performed based on the generated reconstructed PETimage. In other embodiments, the normalizing factor of the detectorefficiency may be generated by using the data of the phantom obtained bythe PET data collection method described above.

In some embodiments, there may be tens of thousands of detector units inthe detector 114 of the PET system 100. The detection efficiency of thedetector units may be inconsistent due to their respective geometricpositions and performance differences. The performance differences ofthe detector units may be due to factors including different luminousefficiencies of crystal strips of the detector units, different couplingextents between the crystal strips and photomultiplier tubes in thedetector units, and different angles of the crystal strips with respectto coincidence lines. The inconsistency of the detection efficiency ofthe detector units may introduce artifacts in the PET imagereconstruction. Therefore, to accurately model the detector units and toobtain a satisfactory image quality, the detection efficiencies of thedetector units of the detector 114 may be normalized. The normalizationof the detection efficiencies may also be referred to as a normalizingcalibration. The normalizing calibration method of the detectorefficiency may be illustrated elsewhere in the present disclosure. Insome embodiments, the normalizing calibration method of the detectorefficiencies may include a plurality of factors (e.g., a plurality ofnormalizing factors), which may be stored in a computer in a fileformat. In some embodiments, while a patient is scanned by the PETsystem 100, the normalizing factor may be applied to a measured value ofthe detector 114 to perform the normalizing calibration of the detectorefficiency.

FIG. 13 is a flowchart illustrating an exemplary process for controllinga phantom of a medical imaging device with a first motion controlleraccording to an embodiment of the present disclosure. Refer to FIG. 13,in 1302, a phantom may be mounted on a phantom controlling device (orreferred to as the second moving mechanism). In 1304, the phantomcontrolling device may be mounted on the scanning table 112 to cause thephantom to insert into the detection region 113. In 1306, the phantommay be controlled to move inside the detection region 113 via thephantom controlling device and the scanning table 112. In someembodiments, the phantom controlling device may include a movingmechanism that may drive the phantom to move along the X directioninside the detection region 113. In some embodiments, the scanning table112 may include a scanning-table driving mechanism (or referred to asthe first moving mechanism) that may drive the scanning table 112 tomove along a forward-backward (e.g., the Y direction shown in FIG. 1)and/or an up-down direction (e.g., the Z direction shown in FIG. 1). Themoving mechanism may move along the he Y direction and/or the Zdirection inside the detection region 113 based on the effect of thescanning-table driving mechanism. In other embodiments, the phantom maybe controlled to move circumferentially inside the detection region 113via the phantom controlling device and the scanning table 112.

FIG. 14 is a schematic diagram illustrating a phantom controlling device(or referred to as the first phantom controlling device, or the secondmoving mechanism) according to an embodiment of the present disclosure.Referring to FIG. 14, the phantom controlling device may include aphantom bearing 1407 and a moving mechanism. The moving mechanism mayinclude a support plate 1401, a first rotation wheel 1402 and a secondrotation wheel 1403 which are installed at both ends of the supportplate 1401, a transmission belt 1408 sheathed on the first rotationwheel 1402, and the second rotation wheel 1403. The transmission belt1408 may extend along the X direction. The phantom 1410 may be connectedto the transmission belt 1408 via the phantom bearing 1407, and thefirst rotation wheel 1402 and/or the second rotation wheel 1403 may beconnected to a driver 1404 (e.g., a first driver). When the driver 1404is started, the first rotation wheel 1402 and the second rotation wheel1403 may drive the transmission belt 1408 to move along the X directionand the phantom 1410 may be moved with the transmission belt 1408 alongthe direction. The phantom 1410 may be driven to reciprocate along thedirection. In one embodiment, the first rotation wheel 1402 and thesecond rotation wheel 1403 may be mounted on the support plate 1401 viaa supporting frame, and the transmission belt 1408 and the firstrotation wheel 1402 and the second rotation wheel 1403 may begear-driven. In another embodiment, the moving mechanism may include aguide structure, and the phantom 1410 may be connected to the guidestructure via the phantom bearing 1407 (e.g., a connecting plate) andmay move along the guide structure. In a specific embodiment, the guidestructure may be a guiding mechanism 1405 installed on the support plate1401, and the guiding mechanism 1405 may be installed on one side of thetransmission belt 1408 and may extend along the X direction. The guidingmechanism 1405 may be installed with a slider block 1406. The phantom1410 may be mounted on the connecting plate 1407. One end of theconnecting plate 1407 may be connected to the slider block 1406 and theother end thereof may be connected to the transmission belt 1408. Thephantom 1410 may move along the guiding mechanism 1405, along with thetransmission belt 1408.

FIG. 15 is a schematic diagrams illustrating a phantom controllingdevice (or referred to as a first phantom controlling device, or thesecond moving mechanism) according to another embodiment of the presentdisclosure. Referring to FIG. 15, the phantom controlling device mayinclude a phantom bearing 1507 (e.g., a connecting plate) and a movingmechanism. The moving mechanism may include a support plate 1501 and ascrew shaft 1502 installed on the support plate 1501. The screw shaft1502 may extend along the X direction (e.g., a direction perpendicularto the axial direction of the detection region 113). The phantom 1510may be mounted on a support base 1503 via the phantom bearing 1507, thesupport base 1503 may be sheathed on the screw shaft 1502, and the endof the screw shaft 1502 may be connected to a driver 1504 (or referredto as a second driver). When the driver 1504 is started, the screw shaft1502 may drive the support base 1503 and the phantom 1510 to reciprocatealong the X direction. In one embodiment, the screw shaft 1502 may bemounted on the support plate 1501 via the supporting frame. In anotherembodiment, the moving mechanism may include a guide structure, and thephantom 1510 may be connected to the guide structure via the phantombearing 1507 and may move along the guide structure. In a specificembodiment, the guide structure may be a guiding mechanism 1505installed on the support plate 1501. The guiding mechanism 1505 may beinstalled on one side of the screw shaft 1502 and may extend along the Xdirection. A slider block 1506 may be installed on the guiding mechanism1505. The phantom 1510 may be mounted on the connecting plate 1507. Oneend of the connecting plate 1507 may be connected to the slider block1506, while the other end thereof may be connected to the support base1503. The phantom 1510 may move along the guiding mechanism 1505 withthe rotation of the screw shaft 1502. In some embodiments, the guidingmechanism 1505 may be installed beneath the screw shaft 1502 and thesupport base 1503 may be mounted on the guiding mechanism 1505. A groovemay be installed on the surface of the support base 1503 facing theguiding mechanism 1505, so that the support base 1503 may slide alongthe guiding mechanism 1505.

The moving mechanism may drive the phantom 1510 to move along the Xdirection inside the detection region 113. The movement may be of auniform or non-uniform velocity, may be a continuous movement within acertain period of time, or may be a discontinuous movement separated byat least one time interval. The present disclosure is not intended tolimit the scope of the mode in which the moving mechanism may drive thephantom 1510 to move along the X direction inside the detection region113.

FIG. 16 is a schematic diagrams illustrating a phantom controllingdevice according to another embodiment of the present disclosure. Asillustrated, the phantom controlling device may include a support plate1601, screw shaft 1602, support base 1603, driver 1604, guidingmechanism 1605, slider block 1606 and a connecting plate 1607. Thefunction of the phantom controlling device may be illustrated in FIG. 14and/or FIG. 15. The configuration of the connecting plate 1607 and themanner in which the phantom 1610 is located in the connecting plate 1607may be different with respect to those illustrated in FIG. 14 and/orFIG. 15.

The phantom 1610 may be a point phantom, a line phantom, a rod phantom,etc. As shown in FIGS. 14 and 15, the phantom may be a rod phantom. Asshown in FIG. 16, the phantom 1610 may be a point phantom and the pointphantom 1610 may be installed at an end of a connecting plate 1607. Inone embodiment of the disclosure, the angle 1613 between the extensiondirection of the phantom on the connecting plate 1611 and the extensiondirection of the moving mechanism 1612 may be any angle greater thanzero, such as 10 degrees, 20 degrees, 30 degrees or 90 degrees. Inanother embodiment, the phantom 1610 and the connecting plate 1607 maybe detachably connected to facilitate the installment or replacement ofthe phantom 1610. In other embodiments, the phantom 1610 (e.g., a rodphantom) or the connecting plate 1607 may be connected to a rotationmechanism (not shown). When the phantom is required for scanning, therotation mechanism may be operated so that the angle 1613 between theextension direction of the phantom 1611 and the extension direction ofthe moving mechanism 1612 may be greater than zero. When the phantom isnot required, the phantom may be rotated so that the extension directionof the phantom may be the same as that of the moving mechanism, so thatthe phantom and the moving mechanism may be accommodated in the shieldcover for storage.

The motion control of the phantom in the Y1 direction as shown in FIG. 1or FIG. 16 may be achieved by the above-described phantom controllingdevice. The phantom controlling device may be placed on the scanningtable 112. In some embodiments, the phantom controlling device may beplaced on the top surface of the scanning table 112 near a frame (e.g.,the gantry 111 of the PET system 100). The support plate 1601 may beinserted directly into a head support socket of the scanning table 112to be fixed onto it. The phantom 1610 mounted on the phantom controllingdevice may be inserted into the detection region 113 by adjusting theposition of the scanning table 112. The phantom controlling device maydrive the phantom 1610 to move along the X direction (e.g., a directionperpendicular to the axial direction of the detection region 113) insidethe detection region 113. The position of the phantom 1610 in adirection perpendicular to the Z direction of the detection region 113may also be adjusted to meet the requirements for precise positioning ofthe phantom 1610. The driver may also be adjusted to meet therequirements to achieve a certain motion trail of the phantom 1610. Forexample, in the PET resolution test, the above-described phantomcontrolling device may position the phantom 1610 at different positionsto meet the requirements for precise positioning of the phantom 1610. Inaddition, the phantom controlling device may drive a rod phantom 1610 tomove along the X direction to simulate a plane phantom.

In some embodiments of the present disclosure, the scanning table 112may include a scanning table driving mechanism that may drive thescanning table 112 to move along the Z direction and/or the Y direction.The scanning table driving mechanism may drive the moving mechanism tomove inside the detection region 113. The movement of the movingmechanism may be of a uniform or non-uniform velocity, may be acontinuous movement within a certain period of time, or may be adiscontinuous movement separated by at least one time interval. Thepresent disclosure is not intended to limit the scope of the mode inwhich the scanning table moving mechanism drive the moving mechanism.

The phantom may move in a certain direction, or in a certain plane whiledriven by the phantom controlling device and/or the scanning table 112.For example, the phantom controlling device (or the scanning table 112)may drive the phantom to move along the X direction or the Y direction.As another example, the scanning table 112 may drive the phantomcontrolling device to move along the Y direction and/or the Z direction.As another example, the phantom controlling device may drive the phantomto move in the X direction, while the scanning table 112 may drive thephantom to move in the Y direction, resulting in a movement in the X-Yplane of the phantom. The movement trail of the phantom may be regularor irregular in shape. For example, the movement trail of the phantommay be circular.

FIG. 17 is a schematic diagram illustrating a circular movement trail ofthe phantom according to some embodiments of the present disclosure.

Referring to FIG. 17, the phantom 1710 may move in a circular trail 1701on the X-Y plane, around the Z axis. The phantom 1710 may move in acircular trail 1701 at a uniform velocity when the equation (2) toequation (5) are satisfied:v _(x) =v×sin θ=rw sin(wt),  (2)v _(y) =v×cos θ=rw cos(wt),  (3)v=rw,  (4)θ=wt,  (5)wherein v denotes the uniform velocity of the phantom 1710, and wdenotes an angular velocity of the phantom 1710, and θ denotes an anglebetween the axis of the phantom 1710 and the Z direction. Vx denotes avelocity of the phantom in the X direction. The phantom 1710 may bedriven by the moving mechanism. Vy denotes a velocity of the phantom inthe Y direction. In some embodiments, a vertical lifting mechanism inthe scanning table 112 may be utilized to drive the phantom 1710 to movein the Y direction.

The movement of the scanning table 112 and the phantom 1710 controllingdevice may be of a uniform or non-uniform velocity. In some embodiments,to obtain a circular movement of the phantom 1710, the speed of thephantom 1710 may be precisely controlled to be uniform during itsmovement. In some embodiments, the scanning table driving mechanismand/or the phantom controlling device may communicate with a computer tocontrol the movement of the phantom 1710 together. The scanning tabledriving mechanism and/or the phantom controlling device may drive thephantom 1710 to move under an instruction sent out by the computer. Insome embodiments, a movement trail may be input into the computer basedon which one or more instructions may be generated. The computer mayfurther send the generated instructions to the phantom controllingdevice and/or the scanning table driving mechanism to control thephantom 1710 to move in the movement trail that has been input to thecomputer.

FIG. 18A is a schematic diagram illustrating a phantom controllingdevice (or referred to as a second phantom controlling device, or thesecond motion controller) according to some embodiments of the presentdisclosure. As shown in FIG. 18A, the phantom controlling device mayinclude a first shield 1801, a second shield 1802 and a phantom 1810.The phantom 1810 (e.g., a point phantom, a line phantom, a rod phantom,etc.) may be installed in a radiation shielding space formed by thefirst shield 1801 and the second shield 1802 and may stretch out orretract into the second shield 1802. When a subject (e.g., a human body)is scanned by the PET system 100, the phantom 1810 may retract into thesecond shield 1802 to prevent the subject from being affected by theradiation from the phantom 1810. When the PET system 100 is to be testedor calibrated, as shown in FIG. 1, radiations of the phantom may berequired to accomplish the test or calibration. Thus, the phantom 1810may stretch out from the second shield 1802 and extend into thedetection region 113 to radiate the detectors of the PET system.

The phantom controlling device may be mounted beneath the scanningtable. For example, the phantom controlling device may be mounted on thebottom surface of the scanning table 112 that is close to the gantry111.

FIG. 18B is a schematic diagram illustrating an internal structure of afirst shield 1801 according to some embodiments of the presentdisclosure. As shown in FIG. 18B, the first shield 1801 has a firstgroove extending along the Z direction. A screw shaft 1804 may beinstalled in the groove. The phantom 1810 may be installed on a sliderblock 1806 that is sheathed on the crew shaft 1804. One end of the crewshaft 1804 may be connected to a first motor 1805, and the first motor1805 may be installed at one end of the first shield 1801. The firstmotor 1805 may drive the crew shaft 1804 to drive the phantom 1810 tomove via the slider block 1806. In some embodiments of the presentdisclosure, a guide structure (e.g., a guide trail) may be mounted on atleast one surface of the first groove, along which the slider block 1806may slide. The phantom controlling device may further comprise a phantomdriving device. The phantom driving device may include a rotation shaft1811 and a rotation arm 1803. One end of the rotation shaft 1811 mayconnect to a second motor 1809. The second motor 1809 may be installedon the slider block 1806, and may slide along the screw shaft 1804 withthe slider block 1806. For example, the second motor 1809 may locatebetween the first shield 1801 and the second shield 1802. The phantom1810 may be connected to the rotation arm 1803. The second motor 1809may drive the rotation shaft 1811 to drive the phantom 1810 to rotatevia the rotation arm 1803. In some embodiments of the disclosure, therotation arm 1803 may be in a crank structure.

FIG. 18C is a schematic diagram illustrating a second shield accordingto some embodiments of the present disclosure. FIG. 18D is across-sectional view of the second shield according to some embodimentsof the present disclosure. As shown in FIGS. 18C and 18D, the secondshield 1802 may have, on its surface facing the phantom 1810, a secondgroove 1807 that extends along the Z direction. The end of the secondgroove, which faces the Y-Z plane, may include an opening. The secondgroove 1807 may provide the phantom 1810 with a moving passage. Themotor 1805 may drive the phantom 1810 to stretch out or retract into thesecond shield 1802 through the second groove 1807. A third groove 1808,which may be configured to accommodate the phantom 1810, may locate on asurface of the second groove 1807. In some embodiments of the presentdisclosure, the third groove 1808 and the second groove 1807 may be ondifferent planes. The third groove may include two closed ends. The twoends of the third groove may be along the Z direction. The phantom 1810may retract into the second shield 1802 and may be accommodated in thethird groove 1808, while the human body is scanned by the PET system100.

To calibrate the PET system 100 with the phantom 1810, the first motor1805 may drive the phantom 1810 to stretch out from the second shield1802 to extend into the detection region 113. The second motor 1809 maydrive the phantom 1810 to rotate at a uniform velocity inside thedetection region 113 to irradiate the detector units within thedetecting region 113. When the calibration of the PET system isfinished, the first motor 1805 may drive the phantom 1810 to retractinto the second shield 1802. The second motor 1809 may drive the phantom1810 to enter a space formed by the third groove 1808 in the secondshield 1802. The space may shied radiation emitted by the phantom 1810.In some embodiments, the phantom controlling device may further includea fixing device for fixing the phantom controlling device on the bottomsurface of the scanning table 112. The fixing device may include abuckle, a nut, or the like, or any combination thereof.

In some embodiments, the scanning table 112 may further include alifting device, through which the height of the scanning table 112 maybe adjusted. When the PET device is calibrated using the phantom, theheight of the scanning table 112 may be adjusted to coincide the axis ofthe rotation shaft 1811 and the axis of the ring of the FOV.

It should be noted that the flowchart described above is provided forthe purposes of illustration, not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations and modifications may be reduced to practice in thelight of the present disclosure. However, those variations andmodifications do not depart from the scope of the present disclosure.For example, the phantom controlling device may not only be used tocalibrate a single modality imaging system such as the PET system 100 asillustrated, a Computed Tomography (CT) system, a MR (MagneticResonance) system, or the like, but may also be used to calibrate amulti-modality imaging system such as PET-CT device, PET-MR device, etc.

Having thus described the basic concepts, it may be rather apparent tothose skilled in the art after reading this detailed disclosure that theforegoing detailed disclosure is intended to be presented by way ofexample only and is not limiting. Various alterations, improvements, andmodifications may occur and are intended to those skilled in the art,though not expressly stated herein. These alterations, improvements, andmodifications are intended to be suggested by this disclosure, and arewithin the spirit and scope of the exemplary embodiments of thisdisclosure.

Moreover, certain terminology has been used to describe embodiments ofthe present disclosure. For example, the terms “one embodiment,” “anembodiment,” and/or “some embodiments” mean that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined assuitable in one or more embodiments of the present disclosure.

Further, it will be appreciated by one skilled in the art, aspects ofthe present disclosure may be illustrated and described herein in any ofa number of patentable classes or context including any new and usefulprocess, machine, manufacture, or composition of matter, or any new anduseful improvement thereof. Accordingly, aspects of the presentdisclosure may be implemented entirely hardware, entirely software(including firmware, resident software, micro-code, etc.) or combiningsoftware and hardware implementation that may all generally be referredto herein as a “unit,” “module,” or “system.” Furthermore, aspects ofthe present disclosure may take the form of a computer program productembodied in one or more computer readable media having computer readableprogram code embodied thereon.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including electro-magnetic, optical, or thelike, or any suitable combination thereof. A computer readable signalmedium may be any computer readable medium that is not a computerreadable storage medium and that may communicate, propagate, ortransport a program for use by or in connection with an instructionexecution system, apparatus, or device. Program code embodied on acomputer readable signal medium may be transmitted using any appropriatemedium, including wireless, wireline, optical fiber cable, RF, or thelike, or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB. NET,Python or the like, conventional procedural programming languages, suchas the “C” programming language, Visual Basic, Fortran 2103, Perl, COBOL2102, PHP, ABAP, dynamic programming languages such as Python, Ruby andGroovy, or other programming languages. The program code may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider) or in a cloud computing environment or offered as aservice such as a Software as a Service (SaaS).

Furthermore, the recited order of processing elements or sequences, orthe use of numbers, letters, or other designations therefore, is notintended to limit the claimed processes and methods to any order exceptas may be specified in the claims. Although the above disclosurediscusses through various examples what is currently considered to be avariety of useful embodiments of the disclosure, it is to be understoodthat such detail is solely for that purpose, and that the appendedclaims are not limited to the disclosed embodiments, but, on thecontrary, are intended to cover modifications and equivalentarrangements that are within the spirit and scope of the disclosedembodiments. For example, although the implementation of variouscomponents described above may be embodied in a hardware device, it mayalso be implemented as a software only solution, for example, aninstallation on an existing server or mobile device.

Similarly, it should be appreciated that in the foregoing description ofembodiments of the present disclosure, various features are sometimesgrouped together in a single embodiment, figure, or description thereoffor the purpose of streamlining the disclosure aiding in theunderstanding of one or more of the various inventive embodiments. Thismethod of disclosure, however, is not to be interpreted as reflecting anintention that the claimed object matter requires more features than areexpressly recited in each claim. Rather, inventive embodiments lie inless than all features of a single foregoing disclosed embodiment.

In some embodiments, the numbers expressing quantities or propertiesused to describe and claim certain embodiments of the application are tobe understood as being modified in some instances by the term “about,”“approximate,” or “substantially.” For example, “about,” “approximate,”or “substantially” may indicate ±20% variation of the value itdescribes, unless otherwise stated. Accordingly, in some embodiments,the numerical parameters set forth in the written description andattached claims are approximations that may vary depending upon thedesired properties sought to be obtained by a particular embodiment. Insome embodiments, the numerical parameters should be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques. Notwithstanding that the numerical ranges andparameters setting forth the broad scope of some embodiments of theapplication are approximations, the numerical values set forth in thespecific examples are reported as precisely as practicable.

Each of the patents, patent applications, publications of patentapplications, and other material, such as articles, books,specifications, publications, documents, things, and/or the like,referenced herein is hereby incorporated herein by this reference in itsentirety for all purposes, excepting any prosecution file historyassociated with same, any of same that is inconsistent with or inconflict with the present document, or any of same that may have alimiting affect as to the broadest scope of the claims now or laterassociated with the present document. By way of example, should there beany inconsistency or conflict between the description, definition,and/or the use of a term associated with any of the incorporatedmaterial and that associated with the present document, the description,definition, and/or the use of the term in the present document shallprevail.

In closing, it is to be understood that the embodiments of theapplication disclosed herein are illustrative of the principles of theembodiments of the application. Other modifications that may be employedmay be within the scope of the application. Thus, by way of example, butnot of limitation, alternative configurations of the embodiments of theapplication may be utilized in accordance with the teachings herein.Accordingly, embodiments of the present application are not limited tothat precisely as shown and described.

We claim:
 1. A method implemented on an imaging device having at leastone processor and storage for medical imaging, comprising: determining aplurality of phantom positions based on a scanning parameter of ascanner and a parameter of a phantom; moving, by a motion controller,the phantom along an axis of the scanner to the plurality of phantompositions; acquiring, by the scanner of the imaging device, a first setof PET data relating to the phantom at the plurality of phantompositions, wherein the length of an axis of the phantom is shorter thanthe length of an axis of the scanner, and at least one of the pluralityof phantom positions is inside a bore of the scanner; and storing thefirst set of PET data as an electrical file.
 2. The method of claim 1,wherein the determining the plurality of phantom positions comprises:determining the plurality of phantom positions based on at least one ofscan time of the scanner, the length of the axis of the scanner, phantomweight and the length of the axis of the phantom.
 3. The method of claim1, further comprising: reconstructing a PET image at least based on thefirst set of PET data.
 4. The method of claim 3, wherein thereconstructing a PET image based on the first set of PET data comprises:extracting a second set of PET data from the first set of PET data basedon the plurality of phantom positions of the phantom, the second set ofPET data corresponding to one or more coincidence events of the phantom;acquiring a first set of attenuation data for the phantom, the first setof attenuation data corresponding to part of the axis of the scanner;determining a second set of attenuation data for the phantomcorresponding to the axis of the scanner based on the plurality ofphantom positions and the first set of attenuation data; andreconstructing the PET image based on the second set of PET data and thesecond set of attenuation data.
 5. The method of claim 3, furthercomprising: acquiring calibration data; and correcting the PET imagebased on the plurality of phantom positions and the calibration data. 6.The method of claim 5, wherein the calibration data comprises nuclidedecay corresponding to the axis of the scanner, and the correcting thePET image based on the plurality of phantom positions and thecalibration data comprises: generating statistic data of phantomposition by normalizing the plurality of phantom positions; generatingstatistic data of nuclide decay by normalizing nuclide decaycorresponding to the axis of the scanner; and correcting the PET imagebased on the statistic data of phantom position and the statistic dataof nuclide decay.
 7. A system for medical imaging, comprising: a bedconfigured to support a phantom; a scanner configured to detectcoincidence events related to the phantom; a motion controllerconfigured to move the phantom along the scanner to a plurality ofphantom positions, wherein the plurality of phantom positions aredetermined based on a scanning parameter of the scanner and a parameterof the phantom; at least one storage medium including a set ofinstructions; and at least one processor configured to communicate withthe at least one storage medium, wherein when executing the set ofinstructions, the system is configured to: acquire, by the scanner, afirst set of PET data relating to the phantom at the plurality ofphantom positions, wherein the length of an axis of the phantom isshorter than the length of an axis of the scanner, and at least one ofthe plurality of phantom positions is inside a bore of the scanner; andstore the first set of PET data as an electrical file.
 8. The system ofclaim 7, wherein the motion controller is further configured to move thebed to drive the phantom to the plurality of phantom positions.
 9. Thesystem of claim 8, wherein the motion controller comprises a firstmotion controller, the first motion controller comprising: a firstmoving mechanism configured to move the bed in a first direction or asecond direction; and a second moving mechanism configured to move thephantom in a third direction, the third direction is perpendicular tothe first direction and the second direction.
 10. The system of claim 9,wherein the second moving mechanism comprises: a support plate; a firstrotating wheel and a second rotating wheel disposed at two ends of thesupport plate; a first driver connected to the first rotating wheel andthe second rotating wheel; and a transmission belt that encompasses thefirst rotating wheel and the second rotating wheel, wherein thetransmission belt extends in the third direction, and is connected tothe phantom.
 11. The system of claim 9, wherein the second movingmechanism comprises: a support plate; a screw shaft disposed on thesupport plate, wherein the screw shaft extends in the third direction; asecond driver connected to an end of the screw shaft; and a support baseattached to the screw shaft, wherein the support base is connected tothe phantom.
 12. The system of claim 9, wherein the second movingmechanism further comprises a guiding mechanism, and the phantom isconnected to and moves along the guiding mechanism.
 13. The system ofclaim 9, wherein the second moving mechanism further comprises a shieldconfigured to shield radiation from the phantom.
 14. The system of claim8, wherein the motion controller comprises a second motion controller,and the second motion controller comprises a moving mechanismcomprising: a screw shaft extending along the first direction, whereinan end of the screw shaft is connected to a first driver; a slider blockattached to the screw shaft, wherein the slider block is connected tothe phantom; and a shield configured to accommodate the screw shaft, theslider block and the phantom.
 15. The system of claim 14, wherein thesecond motion controller further comprises: a rotation shaft; a seconddriver mounted on the slider block, wherein the second driver isconnected to an end of the rotation shaft; and a rotation arm configuredto rotate the phantom under a force supplied by the rotation shaft. 16.The system of claim 14, wherein the shield comprises a first shieldcomprising a first groove, wherein the first groove extends along thefirst direction, and the screw shaft is disposed inside the firstgroove.
 17. The system of claim 16, wherein the shield further comprisesa second shield, a surface of the second field facing the phantomcomprising a second groove configured to provide a moving passage forthe phantom, wherein the second groove extends in the first direction.18. The system of claim 17, further comprising a third groove configuredto accommodate the phantom, wherein the third groove is on a differentplane from the second groove, and extends in the first direction. 19.The system of claim 16, wherein the first groove comprises a guidingmechanism, and the slider block is configured to move along the guidingmechanism.
 20. A non-transitory computer readable medium includingexecutable instructions that, when executed by at least one processor,cause the at least one processor to effectuate a method comprising:determining a plurality of phantom positions based on a scanningparameter of a scanner and a parameter of a phantom; acquiring, by thescanner of the imaging device, a first set of PET data relating to thephantom at the plurality of phantom positions, wherein the length of anaxis of the phantom is shorter than the length of an axis of thescanner, and at least one of the plurality of phantom positions isinside a bore of the scanner; and storing the first set of PET data asan electrical file.